I wouldn't exactly say that evenness is important as long as the curve stays reasonably high. I would regard a lens with MTF 40lp/mm > 50% a very good lens.

This wavy curves normally come from waviness of the field. So if you put focus on the subject, like the eye of the subject, and that part is around 22mm of center sharpness will be improved at that point. But reduced elsewhere. But, absolute sharpness can only exist in a very thin plane, so only the parts of the image having absolute focus are optimally sharp.

This situation is different if you shoot repro, where the whole image is in the same plane or distant landscape, those are the situations where a really flat field helps.

That of course takes us back to focus, I still consider live view necessary for pin point focus accuracy. If you cannot focus exactly great MTF cannot be achieved anyway.

The 55 mm lens is an inverted telephoto (Distagon in Zeiss speak) while the 47 mm is a symmetrical design (Biogon in Zeiss speak). Symmetrical designs usually have less issues with field curvature. Would Schneider not show the 60 lp/mm curve nobody would be complaining.

The curves normally shown used to be either 10, 20, 40 lp/mm or 10 and 30 lp/mm.

The 30 lp/mm curve seems to stay at 70% (varies between 57% and 80%) that is quite decent.

Also, note that the lens has very little astigmatism and very little chromatic aberration. The MTF-curves don't diverge much.

I don't think this is a bad lens.

Schneider is using much higher sets of cycle figures than other manufacturers (60 lppm = 50% > than what most other manufacturers state). Other Distagon designs such as the 50mm lenses from Rollei and Zeiss show similar curve shapes. As Erik stated, it's the nature of the lens design. As to new vs older lens designs, many older lenses like the Zeiss Biogon 38mm designed over 50 years ago have barely improved, and mostly due only to lens coating improvements.

As others have said, it's hard to compare graphs from different manufacturers; not only does Schneider use stricter/higher cycle figures, they also provide graphs for 3 different focusing distances (you chose close up focusing) while your graph for the Contax only shows sagittal or tangential without knowing which at some unknown focusing distance.

Since you didn't answer how you calculated the averages I'll assume you eyeballed it with Microsoft Paint. Looking at dozens of MTF graphs it appears that contrast fall off is not proportional to a decrease in cycles/mm so your extrapolations are quite likely inaccurate and not very meaningful. Why you even bother is beyond me. I still shoot film so I'm pretty unbiased but reading your comments on this forum it seems like you jump on every chance you get to bash Phase One - I'm curious why.

Posting MTF charts for 35mm lenses without any context or reference to focal length is also pretty silly. The MTF for the Nikon gives the impression it must be incredibly soft along the edges and based on your extrapolation methods a 60 cycles/mm curve would begin at... 25% ? At 30 lppm the line already drops to 50% halfway through the frame. Nothing like a (Insert token D800 reference here) to take advantage of that lens

As Erik stated, the MTF graphs for the Schneider 55mm are quite good and my 'similarly designed' Hasselbald CF 50mm FLE produces stellar images. The other Phase Schneider lens MTF graphs are excellent and pixelpeeping at the Phase Schneider files on the digital transitions website, the images are very impressive :

The PS 55 also seems to have very good relative illumination across the field with little light fall off around the edges. I'm not sure that consistency is that big of a factor, what the 'rollercoaster' graph tells me is that there is a bit of drop in contrast that picks up again all the way to the outer edges of the frame instead of 'consistently' dropping off a cliff like the Nikon lens.

PS - Could you edit your original post to indicate the contax curves being 10/20/40 instead of 10/20/30 ? It's a bit confusing when comparing the graphs.

As far as I can see it the curve for the Nikon lens is as f/1.4, few lenses really excel at that aperture. I have seen that some test indicating the Nikon is an excellent lens.

Also, I may add that most curves shown may be calculated data instead of measured data. Especially, some curves presented by Sony give me the impression that they have originated in the design departement and not in the lens design departement.

Thanks for chiming in. I feel it's unfortunate the Schneider is getting a lot of flak for presenting honest MTF data, I wish more companies would do that, but that will not happen if we misuse the data to discredit the vendors.

Posting MTF charts for 35mm lenses without any context or reference to focal length is also pretty silly. The MTF for the Nikon gives the impression it must be incredibly soft along the edges and based on your extrapolation methods a 60 cycles/mm curve would begin at... 25% ? At 30 lppm the line already drops to 50% halfway through the frame. Nothing like a (Insert token D800 reference here) to take advantage of that lens

I find it very interesting to read Fred's comments. I think he gets a lot of negative bullshit from those who should know better.

The fact is: The lenses made 10 years ago were just as good, an sometimes better, than the new Phase or Hasselblad H lenses. People don't like to admit that after investing a lot in the "digital" lenses. I am not a tecnical guy like Fred, but I have tested and own a lot of different lenses and backs. From my experience the new Phase lenses are good, but not at all better than the older Hasselblad or Contax lenses.The leaf shutter is of course an improvement for many.

Some of the older lenses can not even be made anymore because they used glas which is now limited because of enviromental issues. Hope everybody understands my english

I find it very interesting to read Fred's comments. I think he gets a lot of negative bullshit from those who should know better.

The fact is: The lenses made 10 years ago were just as good, an sometimes better, than the new Phase or Hasselblad H lenses. People don't like to admit that after investing a lot in the "digital" lenses. I am not a tecnical guy like Fred, but I have tested and own a lot of different lenses and backs. From my experience the new Phase lenses are good, but not at all better than the older Hasselblad or Contax lenses.The leaf shutter is of course an improvement for many.

Some of the older lenses can not even be made anymore because they used glas which is now limited because of enviromental issues. Hope everybody understands my english

You misunderstand my frustration.

I agree: there are many absolutely fantastic older lenses. Newer or more expensive does not necessarily mean better. In fact BCooter loves his (old) lenses and I specifically called out that post as being a post useful to the community.

My point is that anyone who actually understands MTF curves knows it is highly suspect to compare MTFs from different sources, or to draw too broad of conclusions from them. To use them as conclusive evidence for definitive sweeping statements is the worst form of justification-by-technobabble.

I think anybody's critique would have a lot more validity if they didn't go after one brand or format and they would show some "photographs" that are relevant or informing.

Also in every large rental stage I work in, from New York, LA, Milan and Tokyo is a rarity if I don't see one of the world's premier photographers shooting on set with a medium format camera and back, with Phase being the predominate back.

I don't think everyone that uses medium format is wrong or has thrown away their medium cameras for a Nikon.

Anyway, pretty photographs are fun, charts make me sleepy and Fred is capable of taking pretty photos show them and really make a statement.

If I believed every chart, every spread sheet that comes my way, wall street would own my studios, my cars, my clothes my house and my dog.

See is believing.

But for the record I use a contax for digital because at the time the DF wasn't to the level it is today, the H system didn't have their complete integrated approach of camera to back and I'd heard rumblings of Phase and Hasselblad not getting along, so the Contax was the best option for me at the time.

Today who knows?

Doug says the old lenses are good and sure, they are, but the Contax doesn't autofocus as fast as the DF or the H4, that is one thing I've tested. It works, works good and once you learn it's nuances its accurate, but you gotta think about it.

I also find the Contax lenses sharp, usually a little over sharp and brittle and honestly never liked them for transparency film as they are very contrasty, though since digital is kind of broad and flat in the middle they work fine.

But let's also be honest about lenses. Anytime I see a "bad' lens is there usually was some problem in manufacturing or shipping. Any lens that costs more than a pair of converse sneakers is usually sharp and good.

It might have some distortion or fall off at the edges slightly but I don't mind that because I rarely have to worry about edge sharpness and distortion is a batch, easy software fix.

I haven't test every phase/mamiya lens but I doubt very seriously if in todays time a manufacturer that sells high definition still cameras would ship non sharp lenses.

I've got a lot of glass, PL mount RED's, Angenieux, Nikon mounts new, old, Nikon and Zeiss, a box of Canon lenses, some Leica glass even some Voigtlander. For my Contax I have all but the 300 and the zoom (mostly 2 of each) Pentax 6x7 lenses with convertors, Hasselblad lenses with convertors Hartblei with a Contax mount and all are different, in color, tone, look and sharpness and I wouldn't say the lease sharp one is bad, I'd just say it looks different.

This project of about 18 setups was shot with a old Hartblei 45mm tilt shift except one image that I shot with the Zeiss 80mm. (Zeiss on the left and old Hartblei on the right.)

For this project I didn't like the Zeiss lens as I think it's too sharp and too crisp it falls off quickly, but 99% of the world wouldn't pick the old model Hartblei because it's not that sharp and by most pixel examiners they probably wouldn't like it.

BTW: I've never shown these two photos side by side where anyone knew the difference . . . I did but I shot it and I thought there was a difference.

The thing is with digital as with film, every lens, every film (or digital) receptor, every lighting style produces a different effect and the only way I know what lens to pick is from using them.

I know photographers, DP's that swear over certain lenses. They're just completely sure that the Panavision lens toasts a Cooke, a Nikon is better than a Canon, anything Zeiss or Leica rocks and for them and they're 100% correct . . . but for the rest of the world, it's all personal choice.

MTF curves say a lot about a lens. They are actually easy to understand, the higher the better. On the other hand, MTF just tells about sharpness, and that sharpness is only achieved in a single plane of focus. The link below shows the effect of defocus and diffraction for a 100/2.8 macro lens at 3 m. Best aperture is 5.6, going past 5.6 diffraction starts taking it's toll, defocusing 3 cm at 3m looses significant sharpness. What the MTF curve shows is sharpness at optimum aperture and exact focus. (Well, the curves are often given for maximum aperture and optimum aperture or f/8).

When shooting landscape at infinity at optimum aperture we do approach the MTF data. Also if we achieve optimal focus in a single point (or plane) we approach the MTF data. But for real 3D subjects at close and intermediate distances most of the subject will be slightly out of focus. Optical designers live by MTF curves but they probably calculate dozens or even hundreds of them. They calculate MTF for different amount of defocus, for instance.

An excellent MTF curve doesn't say that a lens makes good images or even sharp images. A lens with a really bad MTF curve cannot achieve brutal sharpness, but in many cases that may not be needed.

The Zeiss publication appears to be interesting reading. It's more than I can digest with a full plate, so I'll need to spread it out over a period of time. Thanks for the link and know that your intelligent comments are educational.

When I am in the market for a lens, though I have peeked at MTF charts on occasion, I would rather see images (when possible) made with lenses similar to how I plan to use a lens. Of course, I am interested in crispness, contrast, falloff, rendition and bokeh, but I am most interested in the "look" that a lens provides.

Once I have zeroed in on a particular model I have always believed it was necessary to test the lens, or multiple copies when that is possible (decreasingly so today) under the conditions that I plan to use it. I won't purchase a lens anywhere that I cannot return it within at least seven days.

While I don't have a "ton" of lenses, those that I do own are pleasing to me irregardless of what the MTF charts might reveal.

I find it very interesting to read Fred's comments. I think he gets a lot of negative bullshit from those who should know better.

The fact is: The lenses made 10 years ago were just as good, an sometimes better, than the new Phase or Hasselblad H lenses. People don't like to admit that after investing a lot in the "digital" lenses. I am not a tecnical guy like Fred, but I have tested and own a lot of different lenses and backs. From my experience the new Phase lenses are good, but not at all better than the older Hasselblad or Contax lenses.The leaf shutter is of course an improvement for many.

Some of the older lenses can not even be made anymore because they used glas which is now limited because of enviromental issues. Hope everybody understands my english

Hi Henrik -

I agree - there is no reason to cast older lenses in a negative light, there are many strong performers and good glass is good glass. The one area where newer lenses usually outperform is with respect to chromatic aberration, and of course high sync speeds with certain leaf shutters, etc.

But back to the Schneider 55mm and its wavy charts. We compared this lens against the Hasselblad 60mm/3.5 CB Lens. While they appear equally sharp (and equally focused) in the center, the edges are a different story. All 4 edges look equally similar wit each lens. Draw your own conclusions. Raws are available upon request.

This isn't to make any point about old vs new (I'm in favor of both - if they are both good), other than a response to the hand wringing over the charts.

Again - they're not meant to definitively say how great the Schneider 55 is or how average the Hasselblad 60 is. I think anyone that approaches lenses with a fair and open mind will understand that there are few absolute rules on old vs new lenses. And really, this example is meant more to show real world performance in light of the wavy MTF charts - and in light of the concept of using a medium lens as a portrait lens or a non-flat field lens. I didn't check, but I wonder what the MTF chart for the Hasselblad 60mm lens looks like.

I also have a comparison between the Contax 80/2 and the Hassleblad HC 80/2.8. They are much closer in performance, so again it's not about newer being better than older.

Thanks for sharing. Depending the size of the sensor and the crop position it is possible that your crops don't cover the area where the Schneider has it's minimum. The Distagon also has some waviness. See samples below. Both Schneider and Distagon have their minimum at around 22 mm of center. It's hard to compare the graphs as they cover different frequencies.

In the corners the Schneider recovers while the Hasselblad lens drops. So I would expect the Schneider to be much better in the corners on non cropped MF. If we look at the minimum MTF the Schneider perhaps would give 44 % at 40lp/mm (by linear interpolation). Pretty much like the Distagon 60.

The Zeiss Distagon 35/2 ZF.2 has also some waviness, at 15 mm of center it would have around 50% MTF according to Zeiss MTF graphs, but that performance would be reached by f/4. The 35/2 ZF.2 is a 135 format lens.

The Hasselblad HC50II has also some waviness. It comes in at around 55-60 at 40 lp/mm. About the same as the Schneider, if I may guess.

I agree - there is no reason to cast older lenses in a negative light, there are many strong performers and good glass is good glass. The one area where newer lenses usually outperform is with respect to chromatic aberration, and of course high sync speeds with certain leaf shutters, etc.

But back to the Schneider 55mm and its wavy charts. We compared this lens against the Hasselblad 60mm/3.5 CB Lens. While they appear equally sharp (and equally focused) in the center, the edges are a different story. All 4 edges look equally similar wit each lens. Draw your own conclusions. Raws are available upon request.

This isn't to make any point about old vs new (I'm in favor of both - if they are both good), other than a response to the hand wringing over the charts.

This posting is off topic, but gives some insights in modern lens designs, I hope.

Zeiss develops lenses to be used for Nikon, the ZF.2 series, they also develop lenses for Sony. One of the legendary lenses is the 21/2.8 Distagon, a quite complex design with 15 elements in 13 groups. Known to be an outstanding performer.

Zeiss seems to have lot of pride in the new Distagon T* 25/2 ZF.2. This lens has two aspherical surfaces and three lenses with anomalous partial dispersion. Aspheric elements have been around for long but now it is possible to make moulded aspherics although only a few glass compositions can be used for those lenses.

The enclosed figures from that article show the different MTF characteristics of the two lenses. Note that far out corners drop on the 25/2 design. Also the radial and sagittal graphs separate at 40 lp/mm on the Distagon 25/2. This may indicate the lateral chromatic aberration is not fully corrected. This is stated clearly in the article above, but it is also clearly said that there is very little color fringing. The remaining color fringing can be removed in raw conversion.

The drop of at the outer corner is an interesting design choice by Zeiss. The sweet spot of the lens is very large and it gives excellent performance over a very large part of the image even at full aperture, but getting corners sharp needs a lot of stopping down.

The Distagon 25/2 also has a floating group which improves performance at close focus distances.

As a final word, once a lens is good enough, and most of them are, the main issue is to hone the skills of the photographer to make best use of the lens. Tripod, MLU, pinpoint focus, that stuff.

Actually the corner sharpness of the Schneider 55 of Steves pic also does not look convincing to me.

For comparison a stiched image by 5D2 + Mirex + the Zeiss Hasselblad CF 50f4 FLE 16mm shifted upwards plus 12mm downwards and two crops at 2/3 image radius (where the MTF drop of the Schneider would be) and at the corner of 16mm shift.

The corner of the 16mm shift refers to an image circle of 72 mm which is already beyond the 645 image circle of 67mm (sensor 54x40mm).

Actually the corner sharpness of the Schneider 55 of Steves pic also does not look convincing to me.

For comparison a stiched image by 5D2 + Mirex + the Zeiss Hasselblad CF 50f4 FLE 16mm shifted upwards plus 12mm downwards and two crops at 2/3 image radius (where the MTF drop of the Schneider would be) and at the corner of 16mm shift.

The corner of the 16mm shift refers to an image circle of 72 mm which is already beyond the 645 image circle of 67mm (sensor 54x40mm).

Chris as I said before (to the "surprise" of some people) the 55mm was designed predominantly as a fast portrait lens for relative close distances. This is the manufacturer's description (the same one I happen to work for...): Minimal distortion wide angle design, provides a normal look, great for editorial portraits and on location lifestyle photography

The 50mm F4 FLE is a general purpose lens that has the floating element which flattens the field for closer distances. It is slower than the 55mm and when challenged with a high MP back it won't be as sharp in the centre of the frame. In my experience it is also a bit more prone to flaring.